1. Field of the Invention
This invention relates to a control system and strategy for controlling the torque produced by a vehicle powertrain consisting of a power source and a transmission to accelerate and brake the vehicle in both forward and reverse directions in accordance with driver demands as expressed through the manipulation of accelerator and brake pedals and a shift lever. The control system regulates the torque delivered to the wheels of the vehicle by controlling the torque produced by the power source, which could be an electric motor or an internal combustion engine, and the gear ratio in the automatic transmission. More particularly, the invention relates to a system for controlling the clutches in an automatic transmission and the torque command issued to a power source torque controller.
2. Description of the Prior Art
Conventional electronic controls for motor vehicle powertrains employ control algorithms whose execution by an electronic computer determines the need for a gear ratio change. Input data used during execution of the algorithms is derived from electrical signals representing vehicle speed, engine speed, gear selector position and throttle setting. However, a more efficient control of a motor vehicle powertrain would result if additional information, such as that derived from manual control of the vehicle operator over accelerator pedal position, the time rate of its application and release, the sense of direction of the power source torque, brake pedal application and release, etc., were available as input information for use while executing the control algorithms.
The control system interprets the driver commands and automatically commands the vehicle subsystems to achieve a desirable driving characteristic. A microprocessor controller might interpret driver commands for acceleration, braking, start-up, shut-down and process the commands to determine appropriate control of an electric motor that powers the vehicle and the powertrain. Signals derived from foot brake operation can be converted for use in regeneration control, whereby dynamic energy of the vehicle normally dissipated by friction at the wheel brakes is used to drive a generator whose output is applied to and stored in batteries for later use to drive the motor.